Sony Music is joining KKR-backed BMG Rights in a bid for Universal Music Group’s Parlophone record label assets. The bid is said to be around $500 million, sources said.

The teaming up of the two companies — just for the bid — has been under discussion for months, sources said, but just entered an offer in the past few days.

BMG is itself a partnership between private equity powerhouse KKR and German media conglomerate Bertelsmann.

Parlophone was founded in Germany while its UK offshoot made the company famous as a jazz label. Today, Parlophone houses artists such as Kylie Minogue and The Pet Shop Boys.

If the joint bid is successful, partnership discussions have focused on splitting Parlophone assets with Sony taking front-line music — that is, current artists — while BMG takes the catalogue.

The news of Sony’s last-minute partnership with BMG was first reported by the Financial Times.

Vivendi’s Universal Music Group is selling EMI’s Parlophone, except its valuable Beatles assets, to satisfy European antitrust regulators after it bought EMI for $1.9 billion.

Len Blavatnik’s Warner Music Group, which passed on an earlier bid for EMI when bidding got too frothy, will compete with Sony-BMG, and with bids from a consortium fronted by “American Idol” creator Simon Fuller and Chris Blackwell, a music entrepreneur who founded Island Records, and Ron Perelman’s investment group, MacAndrews & Forbes.

A Sony spokeswoman declined to comment. Sources say that a winner should be confirmed by as early as next month. Universal has been working with Goldman Sachs to sell Parlophone and smaller related assets.

Sony was previously a partner with Bertelsmann in a venture named Sony BMG Music Entertainment. Sony bought out Bertelsmann’s 50 percent stake five years ago.